QmlDesigner.propertyEditor: avoid warnings about colors

share/qtcreator/qmldesigner/propertyeditor/Qt/ColorGroupBox.qml

@@ -6,7 +6,7 @@ QExtGroupBox {
 
     property var finished;
     property var backendColor
-	property var color: backendColor === undefined ? "#000000" : backendColor.value
+    property var color: (backendColor === undefined || backendColor.value  === undefined) ? "#000000" : backendColor.value
     property var oldMaximumHeight;
 
     property var startupCollapse: selectionChanged === undefined ? false : selectionChanged;

share/qtcreator/qmldesigner/propertyeditor/Qt/StandardTextColorGroupBox.qml

@@ -23,7 +23,7 @@ GroupBox {
             visible: showStyleColor
             finished: finishedNotify
 
-            backendColor: backendValues.styleColor
+            backendColor: (backendValues.styleColor === undefined) ? dummyBackendValue : backendValues.styleColor
         }
 
         ColorGroupBox {
@@ -31,7 +31,7 @@ GroupBox {
             visible: showSelectionColor
             finished: finishedNotify
 
-            backendColor: backendValues.selectionColor
+            backendColor: (backendValues.selectionColor === undefined) ? dummyBackendValue : backendValues.selectionColor
         }
         
         ColorGroupBox {
@@ -40,7 +40,7 @@ GroupBox {
 
             finished: finishedNotify
 
-            backendColor: backendValues.selectedTextColor
+            backendColor: (backendValues.selectedTextColor === undefined) ? dummyBackendValue : backendValues.selectedTextColor
         }
 
     }